The present invention relates to a medium feeding device for feeding a medium such as a printing paper, and an image forming apparatus having the medium feeding device.
A general image forming apparatus includes a medium feeding device that feeds a medium, and an image forming portion that forms an image on the medium using electrophotography. The medium feeding device includes a medium placing plate on which a stack of the media is placed, and a pickup roller provided so as to contact the uppermost medium of the stack on the medium. The pickup roller feeds the media one by one.
In order to ensure that the pickup roller feeds the media one by one, a height of the medium placing plate needs be adjusted. Therefore, there is proposed a medium feeding device including a spring is provided so as to press the medium placing from below, and an elevating arm is provided so as to abut against the medium placing plate from above. The height of the medium placing plate is controlled by driving the elevating arm using an exclusive motor (see, for example, Japanese Laid-open Patent Publication No. 2005-3520264). The medium feeding device further includes a height sensor for detecting a height of the medium placed on the medium placing plate, and a position sensor for detecting a home-position of the elevating arm.
However, the conventional medium feeding device needs to be provided with an exclusive motor for moving the medium placing plate upward and downward.